In recent years, particularly as a key for a vehicle, a keyless entry system has become widespread. Further, in the keyless entry system, it is also common that an entry code is exchanged by short-range wireless communication only by carrying an electronic key and approaching a vehicle without operating the same, so that the door is opened with the electronic key in a pocket. Further, there are various proposals about associating the keyless entry function with a cellular phone. For instance, Patent Document 1 discloses a keyless entry system in which a cellular phone and a vehicle-mounted machine perform short-range communication with each other so as to lock and unlock a door lock mechanism. In addition, Patent Document 2 proposes a car rental system in which a cellular phone having a keyless entry function receives an entry code transmitted from a management server in long distance, so as to open a lock of a cellular phone vehicle.    Patent Document 1: JP-A-2006-60683    Patent Document 2: JP-A-2003-58795